WebUI: Allow rejecting a promise that is returned from cr.sendWithPromise().

ui/webui/resources/js/cr.js

Index: ui/webui/resources/js/cr.js
diff --git a/ui/webui/resources/js/cr.js b/ui/webui/resources/js/cr.js
index 10ecb7d210bf69fcc52217cffeebb1242513e565..c78ab9df7e05a12b5faac72fadb8f8bc2f40edc2 100644
--- a/ui/webui/resources/js/cr.js
+++ b/ui/webui/resources/js/cr.js
@@ -318,9 +318,9 @@ var cr = function() {
   /**
    * The mapping used by the sendWithPromise mechanism to tie the Promise
    * returned to callers with the corresponding WebUI response. The mapping is
-   * from ID to the Promise resolver function; the ID is generated by
+   * from ID to the PromiseResolver helper; the ID is generated by
    * sendWithPromise and is unique across all invocations of said method.
-   * @type {!Object<!Function>}
+   * @type {!Object<!PromiseResolver>}
    */
   var chromeSendResolverMap = {};
 
@@ -334,12 +334,17 @@ var cr = function() {
    * supply any number of other arguments that will be included in the response.
    * @param {string} id The unique ID identifying the Promise this response is
    *     tied to.
+   * @param {boolean} isSuccess Whether the request was successful.
    * @param {*} response The response as sent from C++.
    */
-  function webUIResponse(id, response) {
-    var resolverFn = chromeSendResolverMap[id];
+  function webUIResponse(id, isSuccess, response) {
+    var resolver = chromeSendResolverMap[id];
     delete chromeSendResolverMap[id];
-    resolverFn(response);
+
+    if (isSuccess)
+      resolver.resolve(response);
+    else
+      resolver.reject(response);
   }
 
   /**
@@ -352,11 +357,11 @@ var cr = function() {
    */
   function sendWithPromise(methodName, var_args) {
     var args = Array.prototype.slice.call(arguments, 1);
-    return new Promise(function(resolve, reject) {
-      var id = methodName + '_' + createUid();
-      chromeSendResolverMap[id] = resolve;
-      chrome.send(methodName, [id].concat(args));
-    });
+    var promiseResolver = new PromiseResolver();
+    var id = methodName + '_' + createUid();
+    chromeSendResolverMap[id] = promiseResolver;
+    chrome.send(methodName, [id].concat(args));
+    return promiseResolver.promise;
   }
 
   /**